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Code

selftests/rseq: Fix mm_cid test failure

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Adapt the rseq.c/rseq.h code to follow GNU C library changes introduced by:

glibc commit 2e456ccf0c34 ("Linux: Make __rseq_size useful for feature detection (bug 31965)")

Without this fix, rseq selftests for mm_cid fail:

./run_param_test.sh
Default parameters
Running test spinlock
Running compare-twice test spinlock
Running mm_cid test spinlock
Error: cpu id getter unavailable

Fixes: 18c2355838 ("selftests/rseq: Implement rseq mm_cid field support")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
CC: Carlos O'Donell <carlos@redhat.com>
CC: Florian Weimer <fweimer@redhat.com>
CC: linux-kselftest@vger.kernel.org
CC: stable@vger.kernel.org
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This commit is contained in:
Mathieu Desnoyers 2024-10-08 21:28:01 -04:00 committed by Shuah Khan
parent 34d5b60017
commit a0cc649353
2 changed files with 77 additions and 43 deletions
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110
tools/testing/selftests/rseq/rseq.c
View File

@ -60,12 +60,6 @@ unsigned int rseq_size = -1U;
/* Flags used during rseq registration. */ /* Flags used during rseq registration. */
unsigned int rseq_flags; unsigned int rseq_flags;
/*
* rseq feature size supported by the kernel. 0 if the registration was
* unsuccessful.
*/
unsigned int rseq_feature_size = -1U;
static int rseq_ownership; static int rseq_ownership;
static int rseq_reg_success; /* At least one rseq registration has succeded. */ static int rseq_reg_success; /* At least one rseq registration has succeded. */
@ -111,6 +105,43 @@ int rseq_available(void)
} }
} }
/* The rseq areas need to be at least 32 bytes. */
static
unsigned int get_rseq_min_alloc_size(void)
{
unsigned int alloc_size = rseq_size;
if (alloc_size < ORIG_RSEQ_ALLOC_SIZE)
alloc_size = ORIG_RSEQ_ALLOC_SIZE;
return alloc_size;
}
/*
* Return the feature size supported by the kernel.
*
* Depending on the value returned by getauxval(AT_RSEQ_FEATURE_SIZE):
*
* 0: Return ORIG_RSEQ_FEATURE_SIZE (20)
* > 0: Return the value from getauxval(AT_RSEQ_FEATURE_SIZE).
*
* It should never return a value below ORIG_RSEQ_FEATURE_SIZE.
*/
static
unsigned int get_rseq_kernel_feature_size(void)
{
unsigned long auxv_rseq_feature_size, auxv_rseq_align;
auxv_rseq_align = getauxval(AT_RSEQ_ALIGN);
assert(!auxv_rseq_align || auxv_rseq_align <= RSEQ_THREAD_AREA_ALLOC_SIZE);
auxv_rseq_feature_size = getauxval(AT_RSEQ_FEATURE_SIZE);
assert(!auxv_rseq_feature_size || auxv_rseq_feature_size <= RSEQ_THREAD_AREA_ALLOC_SIZE);
if (auxv_rseq_feature_size)
return auxv_rseq_feature_size;
else
return ORIG_RSEQ_FEATURE_SIZE;
}
int rseq_register_current_thread(void) int rseq_register_current_thread(void)
{ {
int rc; int rc;
@ -119,7 +150,7 @@ int rseq_register_current_thread(void)
/* Treat libc's ownership as a successful registration. */ /* Treat libc's ownership as a successful registration. */
return 0; return 0;
} }
rc = sys_rseq(&__rseq_abi, rseq_size, 0, RSEQ_SIG); rc = sys_rseq(&__rseq_abi, get_rseq_min_alloc_size(), 0, RSEQ_SIG);
if (rc) { if (rc) {
if (RSEQ_READ_ONCE(rseq_reg_success)) { if (RSEQ_READ_ONCE(rseq_reg_success)) {
/* Incoherent success/failure within process. */ /* Incoherent success/failure within process. */
@ -140,28 +171,12 @@ int rseq_unregister_current_thread(void)
/* Treat libc's ownership as a successful unregistration. */ /* Treat libc's ownership as a successful unregistration. */
return 0; return 0;
} }
rc = sys_rseq(&__rseq_abi, rseq_size, RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG); rc = sys_rseq(&__rseq_abi, get_rseq_min_alloc_size(), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
if (rc) if (rc)
return -1; return -1;
return 0; return 0;
} }
static
unsigned int get_rseq_feature_size(void)
{
unsigned long auxv_rseq_feature_size, auxv_rseq_align;
auxv_rseq_align = getauxval(AT_RSEQ_ALIGN);
assert(!auxv_rseq_align || auxv_rseq_align <= RSEQ_THREAD_AREA_ALLOC_SIZE);
auxv_rseq_feature_size = getauxval(AT_RSEQ_FEATURE_SIZE);
assert(!auxv_rseq_feature_size || auxv_rseq_feature_size <= RSEQ_THREAD_AREA_ALLOC_SIZE);
if (auxv_rseq_feature_size)
return auxv_rseq_feature_size;
else
return ORIG_RSEQ_FEATURE_SIZE;
}
static __attribute__((constructor)) static __attribute__((constructor))
void rseq_init(void) void rseq_init(void)
{ {
@ -178,28 +193,54 @@ void rseq_init(void)
} }
if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p && if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p &&
*libc_rseq_size_p != 0) { *libc_rseq_size_p != 0) {
unsigned int libc_rseq_size;
/* rseq registration owned by glibc */ /* rseq registration owned by glibc */
rseq_offset = *libc_rseq_offset_p; rseq_offset = *libc_rseq_offset_p;
rseq_size = *libc_rseq_size_p; libc_rseq_size = *libc_rseq_size_p;
rseq_flags = *libc_rseq_flags_p; rseq_flags = *libc_rseq_flags_p;
rseq_feature_size = get_rseq_feature_size();
if (rseq_feature_size > rseq_size) /*
rseq_feature_size = rseq_size; * Previous versions of glibc expose the value
* 32 even though the kernel only supported 20
* bytes initially. Therefore treat 32 as a
* special-case. glibc 2.40 exposes a 20 bytes
* __rseq_size without using getauxval(3) to
* query the supported size, while still allocating a 32
* bytes area. Also treat 20 as a special-case.
*
* Special-cases are handled by using the following
* value as active feature set size:
*
* rseq_size = min(32, get_rseq_kernel_feature_size())
*/
switch (libc_rseq_size) {
case ORIG_RSEQ_FEATURE_SIZE:
fallthrough;
case ORIG_RSEQ_ALLOC_SIZE:
{
unsigned int rseq_kernel_feature_size = get_rseq_kernel_feature_size();
if (rseq_kernel_feature_size < ORIG_RSEQ_ALLOC_SIZE)
rseq_size = rseq_kernel_feature_size;
else
rseq_size = ORIG_RSEQ_ALLOC_SIZE;
break;
}
default:
/* Otherwise just use the __rseq_size from libc as rseq_size. */
rseq_size = libc_rseq_size;
break;
}
return; return;
} }
rseq_ownership = 1; rseq_ownership = 1;
if (!rseq_available()) { if (!rseq_available()) {
rseq_size = 0; rseq_size = 0;
rseq_feature_size = 0;
return; return;
} }
rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer(); rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
rseq_flags = 0; rseq_flags = 0;
rseq_feature_size = get_rseq_feature_size();
if (rseq_feature_size == ORIG_RSEQ_FEATURE_SIZE)
rseq_size = ORIG_RSEQ_ALLOC_SIZE;
else
rseq_size = RSEQ_THREAD_AREA_ALLOC_SIZE;
} }
static __attribute__((destructor)) static __attribute__((destructor))
@ -209,7 +250,6 @@ void rseq_exit(void)
return; return;
rseq_offset = 0; rseq_offset = 0;
rseq_size = -1U; rseq_size = -1U;
rseq_feature_size = -1U;
rseq_ownership = 0; rseq_ownership = 0;
} }

10
tools/testing/selftests/rseq/rseq.h
View File

@ -68,12 +68,6 @@ extern unsigned int rseq_size;
/* Flags used during rseq registration. */ /* Flags used during rseq registration. */
extern unsigned int rseq_flags; extern unsigned int rseq_flags;
/*
* rseq feature size supported by the kernel. 0 if the registration was
* unsuccessful.
*/
extern unsigned int rseq_feature_size;
enum rseq_mo { enum rseq_mo {
RSEQ_MO_RELAXED = 0, RSEQ_MO_RELAXED = 0,
RSEQ_MO_CONSUME = 1, /* Unused */ RSEQ_MO_CONSUME = 1, /* Unused */
@ -193,7 +187,7 @@ static inline uint32_t rseq_current_cpu(void)
static inline bool rseq_node_id_available(void) static inline bool rseq_node_id_available(void)
{ {
return (int) rseq_feature_size >= rseq_offsetofend(struct rseq_abi, node_id); return (int) rseq_size >= rseq_offsetofend(struct rseq_abi, node_id);
} }
/* /*
@ -207,7 +201,7 @@ static inline uint32_t rseq_current_node_id(void)
static inline bool rseq_mm_cid_available(void) static inline bool rseq_mm_cid_available(void)
{ {
return (int) rseq_feature_size >= rseq_offsetofend(struct rseq_abi, mm_cid); return (int) rseq_size >= rseq_offsetofend(struct rseq_abi, mm_cid);
} }
static inline uint32_t rseq_current_mm_cid(void) static inline uint32_t rseq_current_mm_cid(void)